This invention relates generally to remote indicating magnetic compasses, and more specifically relates to a compass system for providing discrete bearing information at a visually accessible point on an auto dashboard.
Up until the present time, auto compasses have largely been regarded as accessories that are purchased by motorists subsequent to, and separate from the automobile itself. These prior art accessories commonly, for example, are attached to auto windshields or dashboards by means of a suction cup, or by other means. The mounting location is selected as remote as possible from magnetic material, and compensation adjustments may be present which can be manipulated after the compass is installed. These prior installations are in point of fact, unattractive, undependable, and makeshift. They usually are not lighted since carrying wires to the unit from the dashboard requires drilling holes through the dashboard to make an electrical connection. Some units do carry batteries and ON-OFF switch for momentary night viewing, but, as is so with flashlights, the batteries are usually discharged when called upon for service. In consequence of the foregoing factors, it may be observed that present auto compasses are by and large of but limited utility, and indeed tend to be treated by the public, more as a novelty item or conversation piece -- than as valuable aid to the motorist.
In the past, several basic forms of transmitting (remote-indicating) compasses have been developed and described. Reference may be had in this connection, for example, to the treatise MAGNETIC COMPASSES AND MAGNETOMETERS by Alfred Hine, University of Toronto Press, Toronto, Canada (1968). Among other systems described therein, are those which derive a signal from a master compass via magnetic coupling, capactive coupling, resistance coupling, and photo-electric coupling to discs driven by the master compass. All these reported systems are designed to position a repeater compass needle to precisely correspond to the needle position of the master unit, using either open loop or closed loop servo-control techniques. These compasses are, however, high cost precision instruments, not intended or practical for use in auto installations.
In the last-mentioned connection, it is important to appreciate an understanding of the instant invention, that the function of a compass in an automobile installation is distinct from the function performed by a compass in aircraft or marine vessels. In the latter two environments, the instruments are called upon to provide precise bearings, which are absolutely essential for navigation purposes. In the case of the automobile, however, the motorist does not rely upon the compass for precise navigation. On the contrary, the motorist is obliged to follow a road which may meander in various directions. As he proceeds his interest is not, therefore, one in knowing a precise bearing in exact degrees at all times; but rather is one of having sound information regarding his general direction of progression. This in order that he might assure himself that he is proceeding generally where he wishes to go, and also so that he may appropriately alter his course upon unmarked roads or so forth, and yet be assured of his general direction of advance.
In accordance with the foregoing, it may be regarded as an object of the present invention, to provide a magnetic compass system for use in automobiles, which is accurate and dependable, and which is adapted for direct installation on dashboard or the like, whereby such instrument may be readily provided as a factory option at time of automobile assembly.
It is a further object of the present invention, to provide a magnetic compass system, adapted for installation on dashboards of automobiles or the like, which is so constructed as to enable minimization of the magnetic effects induced on the compass by masses of ferromagnetic material in the automobile.
It is a still further object of the present invention, to provide a magnetic compass system for use in automobiles, which includes a dashboard-mounted bearing indicator, provided with illuminated visual displays; which displays further may be in discrete form indicative of the direction of vehicle progression.